Electromagnetic scattering from grassland Part I: A fully phase-coherent scattering model

A microwave scattering formulation is presented for grassland and other sho rt vegetation canopies, The fact that the constituent elements of these tar gets can be as large as the vegetation layer make this formulation problema tic. For example, a grass element may extend from the soil surface to the t op of the canopy, and thus the upper portion of the element can be illumina ted with far greater energy than the bottom. By modeling the long, thin ele ments of this type of vegetation as line dipole elements, this nonuniform i llumination can be accounted for. Additionally, the stature and structure of grass plants can result in situa tions where the average inner-product or coherent terms are significant at lower frequencies. As a result, the backscattering coefficient cannot be mo deled simply as the incoherent addition of the power from each element and scattering mechanism, To determine these coherent terms, a coherent model t hat considers scattered fields, and not power, is provided. This formulatio n is then used to provide a solution to the multiple coherent scattering te rms, terms which include the correlation of the scattering between both dis similar constituent elements and dissimilar scattering mechanisms, Finally, a major component of the grass family are cultural grasses, such a s wheat and barley. This vegetation is often planted in row structures, a p eriodic organization that can likewise result in significant coherent scatt ering effects, depending on the frequency and illumination pattern. Therefo re, a formulation is also provided that accounts for the unique scattering of these structures.